Figure 5.

Diverse Strategies Used to Avoid the Conditioned Arm

(A) Top: schematic of the maze during the conditioning session. Bottom: hierarchical clustering of arm occupancies in the last 5 min of the conditioning session reveals three groups: 4 fish preferring the center, 9 fish not avoiding the conditioned arm, and 27 avoiding fish. Each group is presented as a table, one row per fish. Columns correspond to maze arms (from left to right: the conditioned arm, the preferred safe arm, the other safe arm) and the center. Each cell shows a color-coded occupancy value in the particular compartment of the maze for a particular fish, with the logarithmic blue-to-red color scheme for the maze arms and the gray color scheme for the maze center.

(B) Top: schematic of the maze during the test session. The rows in (A) and (B) correspond to the same fish. Rows within each group are ordered by their similarity to each other in the hierarchical tree in the test session.

(C) Example trajectories of individual fish in the last 5 min of habituation, in the first and last 5 min of conditioning, and in the first and second 5 min of test session. Top: a fish uses the central compartment as a “safe haven.” Upper middle: a non-avoiding fish revisits the conditioned arm despite continued shocks. Lower middle: a fish prefers one safe arm. Bottom: a fish swims in both safe arms. The conditioned arm is depicted with gray background for the habituation session, blue for the conditioning session, and again gray for the test session. The orientation of the conditioned arm varied in the experiments and is shown here on the left for clarity.

(D) Top: schematic of the maze during the conditioning session in experiments with pattern replacement. Bottom: hierarchical clustering reveals three groups: 5 center-preferring, 9 non-avoiding, and 20 avoiding fish.

(E) Top: schematic of the maze during the test session in experiments with pattern replacement. Bottom: occupancies during the test session that correspond to the groups identified in (D).

(F) Example trajectories of individual fish before and after the pattern replacement. Top: a fish prefers the center. Upper middle: a non-avoiding fish. Lower middle: a fish swims in one safe arm before and after the replacement of the conditioned pattern. Bottom: a fish swims in both safe arms before and after the pattern replacement.

See also Figures S2 and S3.